Heat controlling system



April 7, 1942.

M. L. LS N,

HEAT CQNTRQLLINGSYSTEM 7 Fild Oct, 16, 1939 ROOM 72E2M05TAT INVENTOR.

) MET/N L. NEL 0 v niechanism effectively controls the Patented Apr. 7,1942 UNITED] STATES PATENT oFF1cE.

I 2,279,025 HEAT CONTROLLING SYSTEM Martin L. Nelson, Park Ridge, Ill. 1Application October 16, 1939, Serial No. 291mm 13 Claims. morass-9) Oneof the objects of the present invention is the provision of meanswhereby a room thermo-' stat initiates the control of a time elementmechanism and the heating medium and thereafter the heating mediumhydrostat in cooperation with the time element mechanism directly andintermittently controls the heating medium until such time as a changeoccurs in the room thermo stat.

Another object of the invention is the provision of means whereby thetime element mechanism varies the positions in which the hydrostat hasdirect control of the heating medium.

A further object of the invention relates to the means whereby therelationship of the variable positions of the time element mechanism andthe variable positions of the hydrostat is such that intermittentoperations of the heating medium takes place under the joint control ofthe .hydrostat, the time mechanism, and the thermostat to maintain aconstant desired room temperature.

A further feature of the invention relates to the joint control of saidheating medium by the room thermostat and time mechanism in combinationwith a hydrostat which renders said joint control efiective orineffective dependent upon the relative positions of said hydrostat' andsaid timing mechanism.

Another feature relates to arrangements whereby the hydrostat, inaccordance with the heat at the heating medium, changes the positions ofthe timing mechanism in which positions the timing heating medium.

Another feature relates to an improved arrangement whereby the heatingmedium is intermittently operated by the hydrostat and timing mechanismwith a time interval between each operation to permit sufiicient timefor the room on the last cycle operation of the preceding 1 I energized.H indicates, in :itspreferred-form, a magnet for controlling the valvesupplying the fuel to temperature to reach a temperature proportionateto the then prevailing temperature of the heating medium and weatherconditions before the heating medium is again operated so that the roomthermostat, by its operation or nonoperation, determines if anotherheating operation should take place. v

Another feature relates to the series of inter-.

mittent operations of the heating medium until the room thermostat cutsoff the control for more heat and in which the last setting, ortemperature reached by the'heating medium in its last cycle operation ofthe series, determines the cut on temperature point of the heatingmedium for the first cycle operation of a subsequent series. In case afirst series comprise only one cycle operation, then the samepredetermined cut off temperature point for the first cycle operation ofthe next or second series isreestablished.

If a third seriescomprises more thanone cycle operation then a newpredetermined first'cycle.

cut off temperature point for the fourth series is established inaccordance with the temperature reached on last cycle operation ofthethird series. Therefore, the temperature of the heating medium, atits first cycle cut-off point, goes no higher than the temperaturepreviously reached series. In this manner the heating medium is firstoperated toa point which previously gave satisfactory room temperatureand'then, after the interval provided, is additionally operated only incase the roomthermostat calls for more heat. I I

The various features of novelty and invention will more fullyappear fromthe detailed: descrip- I tion taken in connectionrwith the accompanyingdrawing where the preferred form of the invention is shown.

Reierringto the drawing, RT indicates a well known bimetal roomthermostat having a pair 7 of the usual horseshoe magnets for snapaction of the thermostat to the hot and cold'side con- I tacts. Tindicates a transformer for supplying operating current for the motorand relay magnets. Iii indicates a relay having a pair ofmake contacts I3 and a' set of make-break contacts-l4, the armature contacts I3 and I4being operated towards the relay magnet It when. the'latter is theheating medium (not shown) which may be any well-known hot watensteam,or gas heater.-

If desired, I! could also control the draft and damper controls of a hotair furnace.

Associated'with the heating medium is a hydrostat comprising the bellowsB, the controlling expansionbulb EB and the connecting tube 50. Theexpansion bulb EB is closely associated with the heating medium 50 thatthe temperature at V the heating medium-acts directly upon the fluidcontained therein. As is well-known inthe art, the temperature .towhichthe expansion bulb EB is subjected causes variable vapor tension to bemaintained within the bellows'B, tube 50; and

Y expansion bulb EB, all these parts being charged l i with the properamount of volatile fluid suitable for the temperatures'to whichthehydrostatxis to respond. The bellows B acts upon thebellowst 7 arm BAwhich is pivotedat 20 to raise and lower the'right hand end of bellowsarmBAiinaccordthermostat hot contacts are closed thereby indicating thatthe room temperature is at its proper temperatura'the valve circuit isopen hence the valve II is closed, the main gear MG has been driven in acounter-clockwise direction until the point of arm AJ rests on thelowest point of cam C, the limit switch arm LSA has opened'the downmotor contacts I5, the contacts I, 2, 3 are open, and the hydrostatbellows B is in the position shown.- Since the valve'II is closed, thetemperature of the heating medium gradually lowers and therefore thehydrostat bulb B also,

,gradually'lowers bellows arm BA and cam arm "CAand eventually closescontacts 2 and 3 and then] and I when the pivot point I9 is lowered Hsufficiently.

" Assuming now that the room temperature is such ,asitocall for moreheat, in which case the ance with the expansion and contractionofbellows B. The bellowsarm BA is pivotallyconnected at H) and 23 bylink22 to the cam arm CA.

:Thearm BA, link :22, and arm CA is;part of the time element -mechanismwhich also includes the controlcontacts I, 2 and 3;. the adjusting armAJ,limit switch arm LS A for controlling the down and up contacts I5and, the

' reversible motor RM for operatingtl1e train of gearsshown, the shaft,S ,andnthe cam C. The

,motorRM is driven inralclockwiseor'counterclockwise direction torotate, the driving-gear DG,which through'the associated gearing drivesthe gear D; The gear D is -1 oosely mounted on its shaft and carries a,pin M for engaging the arm'L of; pinion Eto cause the rotation of thelatter. The rotation of pinion jE rotates the main gear MG, shaft S,limit switch arm LSA and cam gi aclockwise or counter-clockwisedirection dependent upon the direction of rotation of the m t RM.

, Thecam C, as shown,ha s, a gradually increasing, diameterso as to,lower or raise adjusting arm AJ: aboutfits pivot 2I so as to raise'orlower the P vo P int I Cam a C The, ca a CA is pivotally connected toadjusting arm AJ at I8 and is pivotally interlinked to bellowsarm. BAbylink 22; Aispring II fastened to1 arin CA tends'to lower the left handend of arm CA whenever ith'e variable pivot points It and I9 permit.

thermostat will operate and close its cold contacts and open its hotcontacts. In response to the clgsing ,of its cold contacts thethermostat RT completes thecircuit for operating relay [0 asf ollowszfrom one terminal of transformer T,

opensa point in the motor RM circuit and at its front contacts completesthe circuit for operating the valve magnet I I as follows: fromtransformer 'l', conductors wand 3I, winding of magnet I I, conductor43, front contact I l, conductors 35 and 3.4, cold contact RT, andconductor 33 to transformer '1". The magnet I I in any wellknown manneroperates to open the valve for the heating medium or controls apparatusto start A "pair ,of insulated spring contacts I and Z are mountedonthe' e treme, left-hand endof cam. -armgCAiand areop'ei'ated intocontact with each *other'and contact 3 by the'spring I'I when thevariable pivot points I81a'nd I9 are 'set inffpositions to" permitsuch'action. As :wm be easily understood-from the drawing, the expansionand contraction of B raises and-lowers arm BA and pivot point I9throughflink'22 and'in a similar manner cam C raises and lowers pivotpoint I8 since -tl'ie' arrnAJ is 'pivotally mounted at 2|.

Contact 3 is insulatedly mountediin st'ationary bracket 25; Since pivotpoints I8 and I9 of 'arm CA are variable,-then it is obvious thatcontactI', 2, and

3 are closed and'opened under the joint control of thefhydrostat andcam" C in accordance'with their variable settings.- i

Oneside ofthe transformer T isconnected to relayfiIO, valve I I andmotor RM by wayof conductors 30, 3| and 32while the other'sideof thetransformer T is connected to the room'thermo- I stat at which point itis branched through the hot and cold, contacts to the variouscontrolling contacts as shown.=

Itwill; now be assumedzthat the apparatus is thepqsiit cns Shown-in thedrawing. hB O I theheating; operation of theiheating medium,

As the'heat increases at the heating medium then-pressure in theexpansion bulb increases thereby causing corresponding expansion in thebellows'B, The expansion of bellows B gradually raises the right-handend of bellows arm BA. Due to the :pivoted link ZZ the cam ,arm CA ispivoted about pivot I8 causing the gradual raisingof the left h'and endof arm CA with the resuit that in a predetermined point of bellows Bthesp ringgcpntact l-separates from contact 2 thereby opening theoriginal energizing circuit of relay I6 but this relay is maintained fora short; interval over its previously traced locking circuit throughcontacts} and 3. A further ex-' pansionof, bellows B causes contacts 2and 3 to separate thereby opening the locking circuit of relay [0 Whichaccordingly deenergizes to open the circuit to valve ,II at frontcontacts I 4 and to close the circuit for motor.RM through back contactsI 4 as follows :v transformer T, conductors cause clockwise rotation ofmotorRM, conductor 45, up spring. contacts IGQconductor 44, back con-Pilots I4, conductorsi35 and 34, cold contacts'RT and conductor 33 totransformer T, Theopening of :magnetfl I'closes the valve to cut-off thefuel to'the heating medium or-prevents further heatingof" theheatingmedium inany well-known manner. The operation of the-motor RM in.a

clockwise direction rotates its gear train thereby causing the pin M toengage arm L after a predetermined time dependent upon the speed ofrotation of motor RM and the ratio of the chain of gears for drivinggear D. In case the cold contact of RT is not opened at this point thenfurther rotation of motor RM causes the rotation of pinion E which inturn rotates the main gear MG shaft S, cam C and limit switch arm LSA ina clockwise direction. The rotation of limit switch arm LSA in aclockwise directon closes the down limit contact springs I5 which arewithout effect at this time since the hot contacts of RT are open. Therotation of cam C in a clockwise direction raises the lower point of armAJ thereby gradually raising the righthand end of arm CA, since arm AJis pivoted at 2!. As cam C rotates pivot point I8 of arm CA is graduallyraised until such time as spring contacts I, 2 and 3 are closed. Sincethe other pivot point I9 of cam arm CA is raised and lowered by bellowsarm BA under control of the bellows B it will be seen that the closureand opening of contacts I, 2 and 3 are dependent upon the relativepositions of pivot points I8 and I9 of arm CA.

The closure of contacts I, 2 and 3 again complete the circuit forenergizing relay II] which, upon operating, again locks andagainoperates valve magnet II over the circuit previously described. Thisreoperation of relay III at back contacts I4 opens the circuit to motorRM which stops further rotation of the gear train and cam C. Theoperation of valve magnet II again causes the heating medium to increaseits temperature thereby causing further expansion of the bellows B. Whenthe bellows B expands it raises arm BA and link 22 to raise pivot pointI9 of arm CA. Since the pivot point I8 is temporarily maintained in itslast set position because the motor RM has stopped cam C, the gradualraising of pivot point I9 by the bellows B finallycauses the separationof contacts I, 2 and 3 with the result that relay I0 and valve magnet IIrelease.

At back contacts IAI the motor circuit is again medium. As iswell-known, the hydrostat bellows B may continue to expand for a shortinterval after magnet II releases because of the time lag of temperaturerise on certain types of heating mediums. However, motor RM continues torotate as long as cold contacts of RT are closed and eventually raisespivot point I8 a sufiicient distance with relation to pivot point I3 toagain close contacts I, 2 and 3.

The reclosure of contacts I, 2 and 3 again causes the operation of relayIII and magnet II and opens the motor circuit, the heating medium againcauses further expansion of Buntil the contacts I, 2 and 3 are againopened.

The opening of contacts I, 2 and 3 again release relay I0 and magnet I Ito again rotate the motor until the contacts I, 2 and 3 again close.These cycle of operations continue until such time as the roomtemperature reaches a point to cause the opening of the cold contactsand the closing of the hot contacts of the room thermostat.

It should be stated at this time that after the room temperature hasonce been heated to the desired temperature very fewv if any full cycleoperations as just described are needed to main-; tain a propertemperature.

In'case the'cold' contacts of RT continue closed the cycleope'rationsare repeated until arm AJ restson the highestpoint of cam Cat which point the limit switch arm LSA opens contacts I 6 to preventfurther rotation of motor RM and cam C. Inthis position pivot I8. israised to, its high-. estpoint and since itcan go no higher, thishighest point determines the temperature pointto. which the heatingmedium can be operated to. That is, with I8 at its highest point andpoint I9 being raised by bellows B to a point to cause opening ofcontacts I, 2 and 3 the circuit of relay I0 is maintained open to holdthe circuit of magnet II open thereby preventing further heating. Thispointof operation is very seldom if ever reachedand has been providedonly as a safety measure to prevent overheating to a dangerous point. IV

From the foregoing description it will be seen that as long as the coldthermostat contacts are closed the heating medium is intermittentlyoperated to raise the temperature by cycle operations under the jointcontrol of the heating medium hydrostat and the timing device such asthe motor RM and associated mechanism and'that the timing device allowsa delay so as to enable the room temperature to reach a pointproportionate to the. temperature of the heating medium and prevailingweather conditions before another cycle operation takes place.

As soon as the room reaches the desired temperature, the room thermostatRT operates to open its cold contacts and close its hot contacts. Thisoperation may take place at any point in the cycle of operationspreviously described. In case the cold contacts open at a time whenrelay I0 andvalve magnet II are energized then relay II) and magnet IIare immediately released, magnet II closing the valve to cut off the suply of fuel or to shut the draft and open the check as the case may be.Relay Ill. releases in this case regardless of the position of contactsI, 2 and 3 and since the cold contacts are opened the motor circuit fordriving the motor in a clockwise direction is likewise opened with theresult that the motor is stopped. However, the closure of the hotcontacts of the room thermostat closes a circuit for ooperating themotor RM in a counter-clockwise direction as follows: from transformer'1', conductor 33, hot contacts of RT, conductor 4i, down contacts I5,conductor @L-winding of motor RM, conductors 32, 3| and 30 totransformer T.

cluded in the motor circuit. The rotation of cam C in acounter-clockwise direction gradually lowers adjusting arm AJ therebygradually lowering pivot point I8 of arm CA. Also during this time thebellows B has been gradually lowering arm BA to lower pivot point I9 ofarm CA as previously described. The relative positions of these pivotpoints I8 and I9 may or may not be such as to close contacts I, 2 and 3at a time the hot contacts open and the cold contacts close. In case thecontacts I, 2 and 3 are open at the time the cold contacts close thenthe motor circuit for operating. motor RM in a clockwise direction istermined time.

r perature to open the cold contactsand close the hot.

It hasbeen found under actual working conditions that very seldom ifever more than one cycle operation takes place during normal weatherconditions and that cam C, after .once being set, is very seldom'rotatedin eitherdirection since the hydrostat in cooperation with the roomthermostat maintains the proper temperature in accordance with thesetpositionofcam C, and cam C is only changed. when there has been a changein the general outside temperature, it being remembered that before camC can be changed the gear D must rotate far enough to cause pin M toengage arm L to rotate, pinion E for each reversal of the motor. Sinceit therefore takes considerable time to reset cam Cand thereby changepivot point l8, the hydrostat bellows B alone becomes eiiective to cutoif the heating operation for the first cycle operation of a new serieswhen'the temperature remainsLfairly constant or when it is gettingcolder. Since cam C has not been changed by the time bellows B cuts offthe first cycle of a new series of heating operations then it willclearly be seen that the heating medium is heated to its first cut-offpoint in, this new series to the same cut-off point as previouslyreached in the last cut-ofi point of the series just proceeding this newseries. The bellows B is first operated to exactly the same point aslast previously. reached to cut-ofi the first cycle heating operationwhen the room thermostat again calls for more heat within apredetermined time. Therefore the first cut-ofi point. for the firstcycle operation of a new series is always the same as the last cut-ofipoint previously reached for the preceeding series in case-thevnewseries. of cycle operations occur within a prede- In other words, whenheat is again called for within a predetermined time, the heating mediumis firstheated t0 the same point lastreached which gave the desired roomtemerations when it is getting colder outside or when it remains fairlyconstant. However, there are exceptions to the above and theseexceptions occur whenit is. getting warmer outside and when aconsiderable time elapses before the thermostat again calls for heat.

For example, it will be assumed that theroom thermostat does not callfor heat for aconsiderable time. During this time the motorRM, aspreviously described, is operated for a sufiicient time to cause the pinM ongear D to engagearm L and thereby rotate pinion E. The operation ofpinion E rotates gear MG and shaft S to causev the rotation of cam C inan anti-clockwise direction. This rotation, of cam C lowers arm AJthereby gradually lowering, pivot point: [8 of arm CA. Also during thistime the heating medium is not being heated with the result that thehydrostat bellows B is gradually contracting to lower arm BA and pivotpoint IQ of arm CA. Therefore, whenever sufficient time elapses betweenheating operations to cause themotor RM and cam C to change'the positionof pivot point I'8, the cut-ofi' point is gradually lowered and thecut-off point is then predetermined by the position of pivot l8 at thetime the hot contacts open and the cold contacts close. The opening ofthe hot contacts. stopping further rotation of cam C to maintain pivotI8 in the position last operated to.

In case it gradually gets warmer outside then the thermostat may never.call for more heat or may do so only after a great lapse of time. Since,during this time the hot thermostat contacts are closed the motor RMrotates cam C to gradually lower arm AJ and pivot l8. The cutoff pointto which it is necessary to heat the heating medium is gradually loweredas pivot point I8 is gradually lowered. Therefore, the cut-off point, inthis case, is predetermined by the position reached by pivot 48 at thetime the hot contacts of the thermostat open and the cold contactsclose. In case the hot contacts of the thermostat do not open then asthe motor RM continues to operate limit switch arm LSA opens downsprings I5 to open the motor circuit to stop further rotation of themotor. The circuits and apparatus are now returned to the positionsshown in the drawing and pivot point I8 is at its lowest possibleposition and therefore, the heating medium must be heated to its initialpredetermined or lowest cut-off point as previously described.

Having described the invention, what is considered to be new and isdesired to be protected by Letters Patent is set forth in the followingclaims.

What is claimed is: l

1. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, a thermostat operable in accordance with thetemperature of said space, a relay, a circuit for said relay includingcontacts on said thermostat and a' source of current, electromagneticmeans for operating said heating medium, means associated with saidheating medium and operablein accordance with the heat at the heatingmedium, contacts directly controlled by said last mentioned means forcompleting said relay circuit, contacts operated by said relay forenergizing said electromagnetic means to operate said heating medium anda time element mechanism controlled by said thermostat for operatingsaid directly controlled contacts dependent upon operated position ofsaid last mentioned means.

2. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, a thermostat operable in accordance with thetemperature-of said space, means associated with said heating medium andoperable to variable positions in accordance with the heat at theheating medium, a time element mechanism associated with said lastmentioned means and operable to variable positionsunder control of saidthermostat, a relay, a circuit for said relay including contacts on saidthermostat and a source of current, contacts controlled in accordancewith the variable positions of said time element mechanism and thevariable positions of said last mentioned means for intermittentlycompleting said relay circuit to intermittently energize and deenergizesaid relay, electromagnetic means for operating said heating means tomaintain said space at a desired temperature, and contacts operated bysaid relay for controlling the operation of said electromagnetic means.

3. In a heat controlling system, a space to'be heated, a heating mediumfor heating said space, means for intermittently operating said heatingmedium in a series of heating operations to heat said space, means forstopping said series of heating operations in response to thetemperature of said space reaching a predetermined value, meansefiective in response to the operation of said stopping means forpredetermining the point at which the first heating operation of a'following series of heating operations is to be interrupted, a motorrotated in one direction during each series of heating operations tocontrol said intermittently operated means until the temperature of saidspace reaches said predetermined value, said motor thereafter rotatedinthe reverse direction between each series of heating operations inresponse to the operation of said stopping means, and means for alteringthe point at which the first heating operation of a following series ofheating operations is to be interrupted only in case said motor makes apredetermined plurality of revolutions in the reverse direction before anew heating operation starts.

4. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, means for intermittently operating said heatingmedium in a series of heating operations to heat said space, means forstopping said series of heating operations in response to thetemperature of said space reaching a predetermined value, meanseffective in response to the operation of said stopping means forpredetermining the point at which the first heating operation of afollowing series of heating operations is to be interrupted, amotoroperated in response to the operation of said stopping means, andmeans operative by said motor only after a predetermined plurality ofmotor revolutions for gradually changing the points at which the firstheating operation of a following series of heating operations is to beinterrupted in proportion to the lapse of time after said predeterminedplurality of motor revolutions and the start of the saidfollowing-series of heating operations.

5. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, means for intermittently operating said heatingmedium in a series of cycle operations to heat said space, means forstopping said series of cycle operations in response to the temperatureof said space reaching a predetermined temperature, means forestablishing a definite cut-off point for said heating medium inresponse to the operation of said stopping means, means for starting anew series of cycle operations to operate said heating medium inresponse to the temperature of said space reaching another predeterminedtemperature, and means whereby said heating medium in the first cycleoperation of a operations to provide a time interval between eachheating operation of said heating medium, means forstopping said seriesof cycle operations in response to the temperature of said spacereaching a predetermined temperature, means for establishing a definitecut-off point for said heating medium in response to the operation ofsaid stopping means, means for starting a new series of intermittentcycle operations to intermittently operate said heating medium inresponse to the temperature of said space reaching another predeterminedtemperature, and means whereby said heating medium is always operated inthe first cycle operation of a new series to only the same saidestablished definite cut-01f point as reached in the last cycleoperation of the preceding series of cycle operations.

'7. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, means including a timing device forintermittently operating said heating medium to heat said space in aseries of heating operations interposed with a time interval betweeneach heating operation, means for stopping said series of heatingoperations in response to the temperature. of said space reaching apredetermined value, means effective in response to the operation ofsaid stopping means for predetermining the point at which the firstheating operation of a following series of heating operations is to beinterrupted, a motor operated in response to the operation of .saidstopping means, and means operative by said motor only after apredetermined plurality of motor revolutions for operating said timingdevice to render said last predetermining means ineffective and forthereafter changing the points at which the first heating operation of afollowing series of heating operations is to be interrupted inaccordance with the lapse of time 7 arm pivoted near its center, one endof said timing arm with respect to said connecting link and bellows armand for pivoting said contact arm at said connecting link to raise andlower said other end of said contact arm, means for controlling saidheating medium, and circuit means including contacts controlled by theraising and lowering of said other end of said contact arm forcontrolling said heat controlling means and said timing means.

9. In a heat controlling system, a space to be heated, a heating mediumfor heating said space, a thermostat operable in accordance with thetemperature of said space, an arm having two pivot points, one end ofsaid arm being free to move, the other end of said arm being the firstof said pivot points and the second pivot point being. located betweenthe ends of saidarm, means controlled by the heat produced. at saidheating medium for raising and. lowering said second pivot point topivot said arm at said first pivot to raise'and lower the free end. ofsaid arm to variable positions, timing. means for raising and loweringsaid first pivot point to pivot said arm at said second pivot point toraise and. lower the free end of said arm to variable positions, meansfor controlling said heating medium, and circuit means includingcontacts on said thermostat and contacts controlled by the free end ofsaid arm in its variable positions for controlling -said' heatcontrolling means and said timing means.

10. In a heat, controlling system, a space to be heated, a heatingmedium for heating said space,

electromagnetic means for controlling said heat.-

ing medium, a circuit. for said electromagnetic means, a thermostathaving contacts. operable in accordance withthe temperature-of. saidspace, a relay, a circuit for said relay including said thermostatcontacts and a source ofcurrent connected to said thermostat contacts,heatresponsive means associated with said heating medium and operable inaccordance with the heat at said heating medium, contacts directlycontrolled by said heat responsive means for completing said relaycircuit, contacts operated by said relay and said thermostat contactscompleting said electromagnetic means circuit'for operating saidlelectromagnetic means to. operate said heating medium, a time. elementmechanism also controlling said directly controlled contacts alternatelywith said heat responsive means, and a circuit for-said time elementmechanism including said thermostat contacts. and contacts con.- trolledby saidrelay whereby said heating medium and. said. time elementmechanism are intermittently and. alternatively operated under control'of. said relay and thermostat contacts, and said I relay. is operatedunder control of said thermostat and said directly controlled contacts.

. 11. In a heat controlling system, a spacetobe heated, a heating mediumfor heating said space,

a thermostat operable in accordance with the controlling the. operationof. said relay in. case said. thermostatiscalling for more heat. tothereby operatesaid heating medium, means directly operated by said.heat responsive means in re.-

relay in case said thermostat is still calling for moreheat, thereoperationof said relay stopping the operation of saidmechanism andcausing the reoperation of said heating medium whereby successiveheating operationsfollowed by successive timing cycles continue untilsaid thermostat no longer calls. for more heat, and contacts on saidthermostat for preventing the operation of said relay inresponse tothetemperature of. said space reaching. the. desired point irrespective ofthe opened or closed condition of said first mentioned contacts.

12. In a heat controlling system, a space to be heated,;a.heating mediumfor. heating said space, means for. intermittently operating said,heatin medium. to heat said. space in. a seriesof heating, operations,means. for stopping said series of heating, operations, in. responsetothe space. temperature; reaching, a predetermined value, meanseffectivein response to. the operation of .said. stopping. means for.predetermining the cut-off point at. which. the first heating operationof a following series is to be interrupted, a first gear train, a motorfor driving saidfirst gear. train, a second gear train. for alteringsaid predetermined cut-ofi point, an arm on said second gear train, apin on said first gear train adapted to drive said second gear train,said motor driving said first gear train and. pin and said second geartrain. by means. of said arm in one direction during each series ofheating operations and driving said first gear train in the reversedirection between each seriesv of. heating. operations, and meanswhereby the pinv on. said first gear train must make one full revolutionin said reverse direction to reengage said arm. on the second gear trainto thereby operatesaid second geartrain and change said predeterminedcut-off point.

13. In a. heat controlling system, a space to be heated, a heatingmedium for heating said space, means. for intermittently operating saidheating medium in a series of heating operationsto heat saidspace, meansfor stopping said series of heating, operations in response. to thetemperature of said .space reaching a predetermined value,

, means effective in response; tov the operation. of

sponse to. an. increase in temperature at. said.

heating medium. for opening said contacts tov rea said stopping meansfor. predetermining the cutoff point. at. which the first. heating.operation of a following series of heating operations-is to beinterrupted, a timing device. operable predetermined distances inaccordance. with its length. of time of operation, saidtiming deviceoperated in response to the operation of said stopping means, and meansfor alteringsaidv predetermined. cut-oiT'point,v said last means. being.nor-.

mally ineffective in response to short timeintervals of operation of.said timing device, and. said last means being effective only in casesaid timing device is operated a definite requireddistance correspondingto a definite predetermined extended time interval.

MARTIN L. NELSON.

